Interference from background noises is one of the main harriers to advance acoustic applications or systems, whether it is audio acquiring microphone systems for communication or automatic speech recognition (ASR), hydrophone systems, sonar systems, or other acoustic systems of the like. The problem has found to be especially difficult with multiple background noise sources that are non-stationary, broadband, bursting and intermittent in a reverberant environment.
For example, in the case of ASR systems, it is increasingly desirable to introduce ASR technology to the large number of mobile communication devices, such as cell phones, car phones, and PDA, recently deployed as a result of the recent rapid advances in mobile communication and related technologies. However, most of these devices are frequently operated in a relatively noisy acoustic environment, such as on the street, in a car, bus, subway, train or airplane, or inside a noisy mall, factory or office. The background noises of these reverberant environments often exhibit the earlier mentioned non-stationary, broadband, bursting and intermittent characteristics. Resultantly, new applications utilizing speech recognition interface, whether for dictation or command-and-control, remain scarce.
To overcome these kinds of noise problems, others have resorted to close-talk handset, headset, or ear-set devices. However, these solutions introduce a number of inconveniences for the users. The wires of these additional headset/ear-set devices are often tangled with other objects. Wireless alternatives are more user friendly, however, they themselves have other limitations and inconveniences, e.g., higher cost. Multi-microphone arrays may avoid some of these limitations, however prior art multi-microphone arrays tend to be physically large, and unsuitable for most applications.
Consequently, there is a need for a more effective solution, especially one that is more compact that can allow a more natural human-machine interface that is hands-free, headset-free, and most importantly noise-free, for certain acoustic applications, such as ASR. In addition, noise reduction and/or cancellation preferably not only increase the clarity and intelligibility of the desired audio, but the reduction/cancellation may perhaps even reduce the load of digital communication networks, thereby resulting in more effective use of their capacities.
Other applications include noise robust headphone, teleconferencing system, digital voice recorder and hearing aid, etc.